[RFC,0/3] KVM: x86/pmu: Add Intel Guest Branch Trace Store Support

Message

Like Xu Sept. 26, 2022, 2:29 p.m. UTC

When we have support for guest pebs, debug store support is implicitly
supported (if there are no hardware surprises). The debug store based
guest bts feature will also come sooner or later, in a very small effort.

One of reasons for adding the RFC tag is that there are currently two paths
for perf to inject interrupts into KVM, and if BTS is added, another one
will be added. This may not end if more perf/kvm interactions are added.

In this patch set I merged Intel BTS with Intel PT's interrupt callbacks as
a first step, but better code could perhaps be tried in the future in two ways:

- Merge KVM's intel_pt codebase into the vPMU framework,  as the previous
  merging effort of guest intel pt is not fully discussed. vPMU will support as
  much as possible the time-sharing multiplexing of host and guest for PMU
  resources (including intel_pt) instead of static partion;
- There is one more, PMI interrupts after forcing KVM to exit, re-traveled
  host idt and assigned to the host handler, then called back to kvm, then
  injected to guest, if there is hardware support and KVM clear judgment,
  interrupts from guest can be injected directly into guest without going
  through the perf subsystem, which will save a lot of overhead.

I'm willing to share more to attract more developers, but the opinions
of the key players are probably more important to the future codebase.

Back to this BTS feature, if there are no blocked comments on this patchset,
more document, selftest and kvm-unit-test will follow obviously.

Like Xu (3):
  KVM + perf: Rename *_intel_pt_intr() for generic usage
  KVM + perf: Passing vector into generic perf_handle_guest_intr()
  KVM: x86/pmu: Add Intel Guest Branch Trace Store Support

 arch/x86/events/intel/bts.c     |  3 +++
 arch/x86/events/intel/core.c    |  2 +-
 arch/x86/include/asm/kvm_host.h |  8 +++++-
 arch/x86/kvm/pmu.h              |  3 +++
 arch/x86/kvm/vmx/capabilities.h |  7 ++++++
 arch/x86/kvm/vmx/vmx.c          | 43 +++++++++++++++++++++++++++------
 arch/x86/kvm/x86.c              |  2 +-
 include/linux/kvm_host.h        |  2 +-
 include/linux/perf_event.h      | 12 +++++----
 kernel/events/core.c            |  9 +++----
 virt/kvm/kvm_main.c             |  6 ++---
 11 files changed, 72 insertions(+), 25 deletions(-)